The initial report that low doses of the NMDA antagonist ketamine had rapid onset antidepressant effects in patients with treatment resistant depression (TRD; Berman 2000) has been confirmed in multiple subsequent studies (Xu 2016). More recently ketamine has been shown to have similar rapid-onset activity in a range of treatment-resistant anxiety (TRA) disorders including Post-Traumatic Stress Disorder (PTSD; Feder 2014), Obsessive Compulsive Disorder (OCD; Rodriguez 2013), Generalized Anxiety Disorder (GAD) and Social Anxiety Disorder (SAD; Glue 2017). All of these studies have used injected ketamine, usually given intravenously. There are preliminary case series data suggesting that oral ketamine has antidepressant effects in patients with TRD (Schoevers 2016). The major side effects of injected ketamine include dissociative symptoms that occur mainly in the first hour after dosing, and minor increases in blood pressure and heart rate, which occur in the first 30 minutes. An oral ketamine formulation could minimize these side effects, and be less onerous/time consuming to administer than injected ketamine.
To explore the potential for an oral ketamine formulation to show activity in patients with TRD or TRA, the inventors developed an extended release ketamine tablet, using a hydrophilic polymeric matrix approach. Polyethylene oxide (PEO) is one of a number of hydrophilic polymers used in controlled drug delivery formulations, and has a number of positive attributes including nontoxicity, high water solubility and swellability (Maggi 2002). Furthermore, tablets formulations based on a high concentration of PEO are able to be annealed (heated) to give tablets of very high hardness that are resistant to crushing. This is a particularly attractive product attribute because ketamine is a drug of abuse. To minimize the potential for dissociative symptoms associated with rapid absorption of ketamine, a prolonged release profile was desirable. The formulation demonstrated linear in vitro dissolution over 10-12 hours. Elimination half-life estimates for ketamine and norketamine for this formulation are much longer that previously reported for tablets.
All references cited herein are incorporated herein by reference in their entireties.